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- Ancillary Targets
- Transient Universe in Stripe 82
- Host Galaxies of SDSS-II SNe
- BCGs in
Stripe 82 - High-Quality LRG spectra
- Reddened
Quasars - No Quasar Left Behind
- Variability-Selected Quasars
- K-band Selected Quasars
- Low-Mass Stars and Brown Dwarfs
- Low-Mass Binary Stars
- White Dwarfs and Hot Subdwarfs
- Distant Halo
Giants - Bright
Galaxies - High-Energy Blazars in Optical
- An X-Ray View Star Formation
- Remarkable X-Ray Sources
- Star-Forming Radio Galaxies
- Galaxies Near QSO Sight Lines
- Luminous Blue Galaxies
- BAL Quasar Variability
- Variable QSO Absorption
- Double-Lobed Radio QSOs
- High-Redshift Quasars
- High-z QSOs in SDSS/UKIDSS
- BOSS Targeting
- Algorithms
High-Redshift Quasars from SDSS and UKIDSS
Summary
Spectra of candidate high-redshift quasars,
Finding Targets
An object whose ANCILLARY_TARGET2 value include one or more of the bitmasks
in the following table was targeted for spectroscopy as part of this ancillary target program.
See SDSS-III bitmasks to learn how to use these
values to identify objects in this ancillary target program.
| Program (bit name) |
Bit in ANCILLARY_TARGET2 | Target Description | Survey Area (deg2) | Target density (deg–2) |
|---|---|---|---|---|
| HIZQSO82 | 0 | Quasar candidate selected with UKIDSS YJHK photometry | 220 | 0.5 |
| HIZQSOIR | 1 | Quasar candidate in SDSS Stripe 82, selected with UKIDSS YJHK photometry | 700 | 0.3 |
Description
This ancillary program described here targets high-redshift quasar candidates through a combination of color cuts combining SDSS ugriz PSF magnitudes and YJHK aperture photometry (with 1" radius apertures) from the UKIRT Infrared Deep-Sky Survey. The addition of infrared photometry from UKIDSS provides leverage to separate quasars at z ~ 5.5 from the red end of the stellar locus. (In fact, the SDSS quasar survey was limited to z < 5.4 by the strong overlap in ugriz colors between high-redshift quasars and red stars.
Primary contact
Ian McGreer |
|---|
| University of Arizona |
| imcgreer -at- email.arizona.edu |
Other contacts
Xiaohui Fan, Linhua Jiang
Target Selection Details
Quasar candidates were selected by matching stellar objects from the SDSS DR7 and UKIDSS DR3 databases. The initial target selection sample is drawn from SDSS with color cuts r - i > 1.4, i - z > 0.5, as well as a magnitude cut of z < 20.2. Likely stars are rejected with the criteria (H - K)Vega < 0.53 or (J - K)Vega < 1.3(Y - J)Vega + 0.32, taking advantage of the fact that quasars are redder than M stars at longer wavelengths and bluer at shorter wavelengths.
The remaining candidates are then prioritized based on izYJK colors. In Stripe 82, the color criteria used for prioritizing targets were slightly relaxed, owing to the coadded ugriz photometry available from Annis et al. (2011), which greatly reduced initial stellar contamination from riz selection. Objects selected with the relaxed criteria on Stripe 82 are given the HIZQSO82 target bit.
REFERENCES
Annis, J.A., Soares-Santos, M., Strauss, M.A., Becker, A.C., Dodelson, S., Fan, X., Gunn, J.E., Hao, J., Ivezić, Ž, Jester, S., Jiang, L., Johnston, D.E., Kubo, J.M., Lampeitl, H., Lin, H., Lupton, R.H., Miknaitis, G., Seo, H-J., Simet, M., & Yanny, B., 2011, arXiv:1111.6619